Study: Sodium’s Effect on Cognitive Function in the Elderly

A variety of factors can influence cognitive function in older adults, but one study published recently in the Journal of Nutrition Health and Aging found that lower sodium intake was associated with worse cognitive function in Southern California community-dwelling older adults over 80 years. In their conclusion, the researchers advised older adults to avoid very low-sodium diets.

While high dietary sodium consumption is linked to hypertension and cardiovascular disease and these conditions themselves have been linked with reduced cognitive function, the role of dietary sodium intake in cognitive aging has not been thoroughly studied independently. Researchers in this study wanted to test if dietary sodium intake would impair cognitive function separately from its effect on blood pressure—which is often the outcome measured in sodium reduction research, such as those with the DASH (Dietary Approaches to Stop Hypertension) diet which focus on low sodium consumption and less cognitive decline as well as other measurements.

While researchers of this recent Southern California study hypothesized that higher sodium intake would be associated with worse cognitive function, male and female community dwellers with an age range of 50 to 96 years didn’t show that higher sodium intake was associated with poorer cognitive performance. Instead, researchers found that lower dietary sodium was associated with poorer performance on cognitive tests independent of lifestyle choices and other factors. Particularly, the association between dietary sodium and executive function was more distinct in those adults who were above 80 years of age.

While this research differs from results of many DASH diet studies and three prior studies, most notably the Canadian NuAge study, direct comparison of results is difficult due to study methodology and population differences. For example, in the Canadian NuAge study, higher sodium intake was associated with a greater three-year decline on cognitive function tests, but only among individuals (67 to 84 years) with low-physical activity levels. Estimates of sodium intake may have systematically differed between the two studies as well.

With the growing number of older adults at risk for cognitive decline, even small changes in cognitive ability associated with dietary sodium intake may have important public health consequences. A 2014 study in the New England Journal of Medicine, reported a J-shaped association of sodium intake with cardiovascular disease and mortality. This study found that individuals consuming more than 6,000 milligrams of sodium per day and those consuming less than 3,000 milligrams of sodium per day both had a higher risk of death and cardiovascular events.

Current recommendations for sodium intake are less than 2,300 milligrams of sodium per day according to 2015-2020 Dietary Guidelines for Americans. In addition, the Institute of Medicine reported that no supporting evidence exists for further reducing the daily sodium intake recommendation to 1,500 milligrams per day in the general population.

What is evident is further research is needed to examine the associations of low to high levels of sodium intake with cognitive function for the elderly — a rapidly growing segment of the population.

 

Journal of Nutrition Health & Aging, “Association Between Dietary Sodium Intake and Cognitive Function in Older Adults,” March 2, 2017. Go to:  https://www.ncbi.nlm.nih.gov/pubmed/28244567

Neurobiology Aging, “Sodium Intake and Physical Activity Impact Cognitive Maintenance in Older Adults: the NuAge Study,” Aug. 19, 2011. Go to: https://www.ncbi.nlm.nih.gov/pubmed/21855174

Canadian Journal of Cardiology, “Assessment of Dietary Sodium and Potassium in Canadians Using 24-Hour Urinary Collection,” June 25, 2015. Go to: https://www.ncbi.nlm.nih.gov/pubmed/26454468

New England Journal of Medicine, “Urinary Sodium and Potassium Excretion, Mortality and Cardiovascular Events,” Aug. 14, 2014. Go to: https://www.ncbi.nlm.nih.gov/pubmed/25119607

Institute of Medicine, “Sodium Intake in Populations: Assessment of Evidence (2013). Go to:
https://www.nap.edu/catalog/18311/sodium-intake-in-populations-assessment-of-evidence

2015-2020 Dietary Guidelines for Americans. Got to: https://health.gov/dietaryguidelines/2015/guidelines/executive-summary/